Rapid detection of pathogenic organisms is important in many applications, including food safety, clinical diagnostics, homeland security and defense. The Centers for Disease Control and Prevention estimates that bacterial infections result in 99,000 deaths a year in the United States, at a cost exceeding $10 billion. Standard methods for identification of bacteria require 24-48 hours and utilize traditional enrichment media and selective culturing on agar plates. While some recent methods have achieved 8-hour detection times for fast growing bacteria such as Escherichia coli, most bacterial species require much longer enrichment times to achieve adequate cell replication to enable accurate detection.
Food processors test large numbers of samples from food processing equipment surfaces, ingredients, raw food and finished product. Faster time to results is the industry's greatest need to minimize risk and cost by providing better control of factory hygiene and food safety, and enabling quicker corrective actions. Furthermore, since inventory is often held until results are available, there is a large incentive for rapid testing to minimize hold times. The cost of food recalls due to potential bacterial contamination can easily reach into the tens of millions of dollars. Rapid identification of bacteria is also a critical capability needed to effectively respond to potential acts of bioterrorism or use of bioweapons during military conflicts.
Detection of extremely low levels of pathogenic bacteria is important for all of these applications. Trace levels of bacteria in food can multiply to dangerous levels during transit, display and storage, and “ready-to-eat” foods like lunchmeat are particularly vulnerable. Listeria is notorious for its ability to continue to multiply even at refrigerated temperatures. Early diagnosis of human infection is needed for effective patient treatment. The consequences of delayed diagnosis can lead to serious health problems or even death. The ability to detect trace levels of bacteria in environmental samples or from air samples will allow identification and accurate geographical delineation of bioagent releases in the event of a terrorist attack or during military operations.
There are currently no means to detect trace levels of bacteria using even the most sensitive molecular approaches, such as polymerase chain reaction (PCR). The need to detect low levels of bacteria requires that an enrichment step be performed to grow the bacteria to a level that is detectable by current instrumentation. Thus, a need exists for methods to rapidly enrich and detect microorganisms.